Do you think elder people have the tendency of talking to themselves?

Have you discovered that some elderly people have this tendency talking to themselves? I don't know whether it is an aged thing that is normal to everyone. I saw a lot of people, especially older people would do something like that. Take my mother for instance, from time to time, while she was washing the dishes, she would like to mumbling on her own, it seems to me that she was talking to herself. Usually, I just leave her alone, and let her be. Sometimes, I was joking with her, ask her who she was chatting to. What do you think?